The Empire's origins are explained in Episode III, where it replaces the Galactic Republic in the midst of a galactic civil war orchestrated by Palpatine, then the Republic's Supreme Chancellor. Palpatine is also secretly the Sith Lord Darth Sidious who intends to purge the Jedi and restore the Sith to power in the galaxy. Palpatine's Sith identity is only known by a small few throughout his life. Palpatine claims that the Jedi attempted to assassinate him and overthrow the Galactic Senate and declares the Jedi to have committed treason. Palpatine declares that the civil war with the separatists in combination with the Jedi coup d'état require the reorganization of the Republic into a state that can provide stability, and a safe and secure society, a Galactic Empire with himself as Emperor. The Senate that he has manipulated overwhelmingly applauds Palpatine's decision.

Emperor Palpatine proceeds to purge the Jedi, who had been the upholders of peace and justice in the Old Republic, and replaces them by redeeming the Sith. Though Palpatine's Sith identity remains a secret to most, his apprentice Darth Vader is the Sith Lord who is publicly known to the galaxy as the ally of Palpatine who is serving the Empire to purge the Galaxy of the Jedi. Vader is the ruthless apprentice of Palpatine who is feared by many in the galaxy. By the time of A New Hope, the Empire has transformed into a fully totalitarian regime, with opposition in the form of the Rebel Alliance.

The Galactic Empire is described in various Star Wars media as a brutal dictatorship, one based on "tyranny, hatred of nonhumans, brutal and lethal force, and, above all else, constant fear."[1]

The Galactic Empire is born out of the collapsing Old Republic. However, the seeds of change are planted during the Clone Wars, the epic war between the Republic and the Confederacy of Independent Systems depicted in Attack of the Clones.

In Episode I, amid a trade dispute, blockade and invasion of Naboo by the Trade Federation, then-Senator Palpatine convinces Naboo's Queen Padmé Amidala to address the Galactic Senate, in order to call for a vote of no confidence in Chancellor of the Republic Finis Valorum's leadership, due to his alleged inability to act quickly to end the occupation of Naboo. The crisis in Naboo allows Palpatine to be elected Chancellor.

When the extent of the Separatist threat becomes clear in Episode II, the Old Republic Senate, the legislature of the Republic, grants Palpatine emergency powers to deal with the crisis. This conflict allows Palpatine to remain in office long after his term as Chancellor officially expires. Palpatine promises to return his powers to the Senate once peace and order is restored to the galaxy. His first order is to create an army of clone troopers resulting in the construction of a massive military. He takes advantage of the conflict to increase the office's power until by Episode III, he is effectively a dictator.

The Jedi begin to distrust the Chancellor's motives, fearing he has come under the influence of a Dark Lord of the Sith named Darth Sidious. Palpatine insists to the Jedi that the war, and thus his emergency powers, will continue until Separatist leader General Grievous is killed. Their concerns are shared by several Senators, who suspect Palpatine may not return his emergency powers to the Senate as promised. Among them are two who had long supported Palpatine, Padmé Amidala and Bail Organa. The film eventually reveals that Palpatine and Sidious are one and the same, and that he has been manipulating the Republic and the Separatists against each other.

When the Jedi Knight Anakin Skywalker discovers Palpatine is actually Darth Sidious, he returns to the Jedi Temple to inform Jedi Master Mace Windu what he has learned. Windu then leaves with three other Masters to arrest Palpatine, instructing Anakin to remain at the temple. Anakin ignores Mace Windu's directive and returns to the Chancellor's office to prevent the Jedi from killing him; Palpatine has manipulated him into believing that he has the power to save Anakin's pregnant wife, Padmé Amidala, from dying in childbirth. Mace Windu, with a cadre of Jedi, enters Palpatine's office and declares that he is under arrest and that the Senate will determine his fate, Palpatine dispenses with his false modest persona and reveals his power-hungry nature, retorting "I am the Senate!". Palpatine quickly produces a lightsaber and dispatches all but Windu. When Anakin arrives, Windu is standing over the disarmed Palpatine, prepared to strike. Anakin intervenes on Palpatine's behalf by cutting off Windu's hand, allowing Palpatine to send Windu plunging to his death with a blast of Force lightning. Anakin then submits to the dark side of the Force, becoming Palpatine's Sith apprentice, Darth Vader.

Palpatine declares the Jedi to be traitors and enemies of the Republic, and issues Order 66, a secret order he implanted in the clones to overthrow their Jedi commanders. Led by Darth Vader, the Grand Army of the Republic, who once took orders from the Jedi, all but exterminate the Jedi Order in a massive galaxy-wide slaughter. Secure in his power and position, Palpatine reorganizes the Republic into the Galactic Empire, with himself as Emperor for life. The Senate enthusiastically supports Palpatine, although a few, like Padmé and Organa, realize that the freedom enshrined by the Republic has been destroyed in the name of a "safe and secure society." A deleted scene in the film establishes that the two are among the main founders of the Rebel Alliance, which later arises in A New Hope.

Two remaining Jedi, Obi-Wan Kenobi and Yoda, attempt to attack and destroy the Sith once and for all. Yoda confronts Palpatine, and Obi-Wan duels his former apprentice, now Darth Vader. Obi-Wan defeats Vader, but Yoda's duel with Palpatine ends in a stalemate and he is forced to flee for his life; both Jedi are forced to go into exile. Padme's children, now motherless and their father a Sith Lord, are placed into adoptive families until such time as the living Force reaches out to them and they take up their destiny.

With the end of the Clone Wars and the formation of the First Galactic Empire, Palpatine rules the Empire with absolute power. He retains the emergency powers that had been voted to him in the years between Attack of the Clones and Revenge of the Sith, allowing him to rule under what amounts to martial law. Vader is the Emperor's second-in-command as well as his chief enforcer. His third-in-command, Sate Pestage, serves as Grand Vizier and runs the Empire day to day. In the 19 years between Revenge of the Sith and A New Hope, Palpatine rules the galaxy from the confines of his heavily guarded palace on Coruscant. During that same time, Vader travels extensively to most of the galactic regions to enforce the Emperor's rule.

The Senate nominally continues to exist, though it is a virtually powerless debating society. Palpatine dissolves the Senate in A New Hope after discovering that several members of the Senate are members of the Rebellion. Aside from Palpatine, the real power in the Empire is in the hands of planetary governors, sector governors (the "moffs") and Grand Moffs overseeing collections of sectors such as the once known as the Outer Rim, and after as the Oversector Outer. After Palpatine dissolves the Senate, the regional governors are formally granted control over their territories.

In A New Hope, Tarkin explains the Empire's philosophy as "rule through fear of force rather than force itself." The instrument of this power is the military, which includes the Imperial Stormtroopers, a massive fleet of starships, and at its zenith the Death Star, a moon-sized superweapon capable of destroying planets. Plans for the Death Star first appear (in universe chronology) in Attack of the Clones; construction begins at the end of Revenge of the Sith.

The Imperial Army is the main ground force of the Galactic Empire. It operates massive ground combat vehicles and maintains garrisons across the galaxy. It also cooperates with other branches of the Empire in a variety of operations. The Imperial Army consists of a considerable number of legions, enough to project power throughout the galaxy. Some of the legions are stationed on the capital planet Coruscant as part of the Emperor's security, while others are scattered in the Imperial Navy and planetary garrisons across the galaxy. Imperial Army officers and crew typically wear the Imperial standard grey uniforms when not clad in armor. Contrary to popular belief, the stormtroopers are not in fact the army, but rather an elite corps that works as a ground force for the Navy—similar to a Marine Corps.

The Imperial Navy, also referred to as the Imperial Starfleet, was the military arm of the Galactic Empire in charge of maintaining security, peace and order in the galaxy. Commanded by Darth Vader, it absorbed the military forces of the Galactic Republic after Palpatine's declaration of the New Order. Organization of the Imperial Navy is assigned to the Moffs.

At its peak, the Imperial Navy fielded millions of warships including the 26,000 "Star Destroyers" that are shown in the film. They fulfilled the Emperor's will throughout the galaxy. After its defeat at the Battle of Endor, the Galactic Empire splits up into warring factions and the Imperial Starfleet splinters along with it. While much of the remnants of the Imperial Navy were later reunited under impressive Imperial commanders, the military organization covered in this article ceased to exist shortly after the death of the Emperor.

Specific responsibilities of the Imperial Navy included defending Imperial citizens from space-based threats such as pirates, smugglers and rebel contingents, enforcing Imperial Will, and overseeing commerce through customs and blockade operations. The Imperial Navy also performs orbital bombardments, transports major ground force deployments and supports them with space and aerial support.

Imperial Navy uniforms come in a variety of designs and colors depending on unit, such as white for intelligence officers, but are usually Imperial standard grey as the rest of the Imperial officer corps.

The Stormtroopers operate with the Navy, and are fielded like marines separate from the army.

The Death Star, a moon-sized space station (the construction of which is in an early stage at the end of Revenge of the Sith) with sufficient firepower to destroy an entire planet, is designed to be the supreme weapon of the Empire's power. Grand Moff Willhuff Tarkin, the station's commander, shortly after informing the heads of the Imperial Military that Palpatine has dissolved the Senate, demonstrates that power in A New Hope, when he destroys Alderaan merely as a show of force. In the film's climactic scene, however, the station is assaulted by a small force of Rebel starfighters; the battle ends with the Death Star's destruction at the hands of Luke Skywalker. The victory is the Rebel Alliance's first major success against the Empire.

A near fatal blow is struck against the Empire in Star Wars Episode VI: Return of the Jedi. In the film's climactic battle, the Rebellion destroys the second Death Star and a number of capital ships that contain a great portion of the Imperial Navy's highest-ranking officers. During this battle, Vader is redeemed by throwing Palpatine to his death, but is mortally wounded by Force lightning intended to kill his son, Luke.

In the Expanded Universe, the Rebels, renamed the New Republic, fight to claim the galaxy from remaining Imperials styling themselves as independent controllers of portions of the galaxy.

In the Jedi Prince novel series, a group of impostors calling themselves the Prophets of the Dark Side install a three-eyed mutant named Trioculus as Emperor by claiming that he is Palpatine's son. By the end of the series, Palpatine's true son, Triclops, helps the Rebels defeat this new enemy.

In the Thrawn trilogy book series, the New Republic is almost brought to its knees by Grand Admiral Thrawn, the new leader of the remnants of the Empire and a military genius. By the time of the third book in the series, Thrawn has nearly defeated the New Republic, but they claim victory in a last-ditch effort, and Thrawn is killed by his own bodyguard, shattering the Empire's unity.

In the Dark Empire comic book series, Palpatine is reborn in a clone body and unites most of the scattered remnants of the Empire, hoping to retake control of the galaxy. By the sequel, Empire's End, he is defeated and destroyed once and for all.

In the novel Darksaber, Admiral Daala, frustrated with the Imperial warlords in the Core fighting and bickering amongst themselves, orchestrates the warlords' deaths and unites and becomes the leader of the remaining Imperial forces. After being defeated in battle once again by the New Republic, she resigns and selects Gilad Pellaeon (originally in the Thrawn Trilogy) as the new leader, where he becomes Grand Admiral Pellaeon.

By the time of the New Jedi Order series, the remaining Imperial military factions sign a truce with the New Republic, becoming the Imperial Remnant. The former enemies then become allies against the invading Yuuzhan Vong. A few years later, the Remnant helped the Galactic Alliance fight an assimilating insect species known as the Killiks, and in the early Legacy era they were a third party in the Second Galactic Civil War but made peace with the Alliance and Confederation all three who where represented by former Imperial commanders.

The Star Wars: Legacy comic book series, set 130 years after the original Star Wars film, explains that, during a civil war, the New Galactic Empire known as the Fel Empire declares war on the Galactic Alliance, the successor state of the New Republic. This conflict begins the Sith-Imperial War, which after three years leads to the eventual defeat of the Galactic Alliance and the Galactic Empire asserting its domination over the galaxy once again. Another split occurs as the Sith Lord Darth Krayt the leader of the One Sith, usurps the throne and forces Emperor Roan Fel to take refuge in the fortress planet of Bastion. The Galactic Alliance Remnant led by Admiral Gar Stazi, Fel's forces known as the Empire-in-exile led by Empress Marasiah Fel and the New Jedi Order led by Jedi Master K'Krukk united against Darth Krayt's Galactic Empire and successfully destroy it and the three united factions formed a new galactic government out of their organisations called the Galactic Federation Triumvirate but the former Empire-in-exile still technically carried on the New Order that Palpatine had created.

Star Wars creator George Lucas sought to make the Galactic Empire aesthetically and thematically similar to Nazi Germany and to appear to be fascist.[2] Like Nazi Germany, the Galactic Empire is a dictatorship based on rigid control of society that dissolved a previous democracy and is led by an all-powerful supreme ruler.[3] The Empire, like the Nazis, desires the creation of totalitarian order[4] and utilizes excessive force and violence to achieve their ends.[4] The name of the Empire's main soldiers, the Stormtroopers, is somewhat similar to the name given to Hitler's Sturmabteilung (SA) paramilitary bodyguards.[3] The visual appearance of Darth Vader in his all-black uniform combined with his devout obedience to the Emperor has allusion to the black-uniformed Nazi Schutzstaffel (SS).[3] The uniforms of Imperial military officers also bear resemblance to uniforms used in Nazi Germany as well as nineteenth-century Germany's ulans (mounted lancers)—who wore a tunic, riding breeches, and boots like the Empire's officers wear—as well as the Imperial officers' cap resembling the field caps historically worn by German and Austrian troops.[5] In addition to Nazi Germany, there was also at least one portion of the Galactic Empire that was based on the Soviet Union, which is the various military personnel and TIE Fighters are flying in formation as Palpatine arrives on the Death Star in Return of the Jedi. George Lucas admitted in the commentary that he based it on the May Day military parades in the Soviet Union.[6]

Palpatine's consolidation of power and declaring himself emperor is like the Roman political figure Octavian (later renamed Augustus), in that Octavian manipulated the Roman Senate as Palpatine did with the Galactic Senate; he legitimized authoritarian rule by saying that corruption in the Senate was hampering the powers of the head of state; he pressured the Roman Senate to give him extraordinary powers as Consul of the Republic to deal with a crisis and he falsely claimed that he would rescind those powers once the crisis was over; and, like the transition of the Roman Republic into the Roman Empire, Octavian, like Palpatine, relied on his strong control over military force.[7]